Note: Descriptions are shown in the official language in which they were submitted.
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THERMOPLASTIC ADSORBENT COMPOSITIONS CONTAINING
WAX AND INSULATING GLASS UNITS CONTAINING
SUCH COMPOSITIONS
BACKGROUND OF THE INVENTION
Recently interest had increased in theromplastic resin systems which
contain desiccants or other adsorbents, especially where the resulting system
is
used to deliver an adsorption and/or desiccation function to an environment.
This interest is especially apparent in the insulating glass industry where
recent technological developments such as those described in U.S. patents
5,313,761 and 5,177,916 have proved to be reliant on the ability to deliver a
flowable, adhesive desiccant formulation in the manufacture of insulating
glass units.
Various formulations have been proposed to meet the needs of the
insulating glass industry. Examples of formulations are disclosed in U.S.
Patents 5,510,416 and 5,632,122 as well as in PCT Published Application WO
96/08541.
While the existing formulations have significant commercial use, there
is a constant desire to improve the formulations by minimizing the amount of
resin component needed to deliver and maintain the necessary amount of
desiccant in the desired location (e.g., adhered to a U-shaped window spacer).
In meeting the need for higher loading/more efficient formulations, it is
generally desirable that the formulations are usable in existing equipment
such
that the implementation of the formulation would not require any additional
expenditure for equipment by the user. Thus, it is highly desirable that the
requirements for handling the formulation (i.e., heating, pumping, applying)
= do not become more severe. This presents a significant challenge in the
context of flowable thermoplastic resin systems since the formulation
viscosity
typically increases sharply as a function of adsorbent loading just above the
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maximum practical loading for the specific formulation. Thus, simply
increasing the amount of adsorbent even in a seemingly minor amount (or
decreasing the amount of resin component) would result in a large increase in
viscosity for the overall formulation at application temperature.
WO 97/00724 discloses adsorbents containing thermoplastic
compositions containing polyolefins and low molecular weight waxes.
However, this reference does not suggest any particular ranges of wax to
accommodate high loadings of adsorbent suitable for applying as a hot melt to
insulate glass units, e.g., compositions which allow adsorbent loadings in the
range of 50-65% by weight adsorbent.
Additionally, it is desirable that the formulation not present any loss of
performance in other aspects which may be important to the specific end use.
Thus, where the formulation is to be used in an insulating glass unit such as
described in the above mentioned patents, the formulation should be resistant
to slump and provide adequate adhesion to the window spacer.
SUMMARY OF THE INVENTION
The invention provides improved thermoplastic adsorbent
compositions which enable reduction in the amount of resin needed to deliver
a given amount of adsorbent without deterioration of viscosity/handling
performance. The invention also provides improved thermoplastic adsorbent
compositions which enable the delivery of a given amount of adsorbent more
reliably and/or under less severe handling/application conditions.
In one aspect, the invention encompasses thermoplastic adsorbent
compositions which contain (a) an adsorbent component and (b) a
thermoplastic organic matrix component containing (i) 2-20% by weight wax,
and (ii) thermoplastic polymer resin, wherein said wax has a weight average
molecular weight of about 800-10000 and is compatible with the thermoplastic
AMENDED SHEEt
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resin (i.e., not prone to phase separation or other adverse interaction when
combined).
In another aspect, the invention encompasses thermoplastic adsorbent
compositions which contain (a) an adsorbent component and (b) a
thermoplastic organic matrix component wherein the composition contains at
least 55 wt.% of adsorbent component and has an apparent viscosity of about 3
x 10G cP or less measured according to ASTM test D-3236-88 at 124 C and
AMENflED SHEE~
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0.125 sec-1 shear rate. The compositions are preferably adhesive and resistant
to slump.
In another aspect, the invention encompasses insulating glass units
containing thermoplastic adsorbent compositions which contain (a) an
adsorbent component and (b) a thermoplastic organic matrix component
containing (i) wax, and (ii) thermoplastic polymer resin, wherein the wax has
a
weight average molecular weight of about 800-10000 and is compatible with
the thermoplastic resin (i.e., not prone to phase separation or other adverse
interaction when combined). Preferably, the adsorbent component contains a
desiccating adsorbent and the formulation desiccates a compartment partially
defined by two or more panes of the insulating glass unit.
The compositions of the invention may also be used for other
adsorption applications. These and other aspects of the invention are
described in further detail below.
DETAILED DESCRIPTION OF THE INVENTION
The invention encompasses thermoplastic adsorbent compositions
containing an adsorbent component dispersed in a thermoplastic organic
matrix component wherein the organic matrix component contains (i) wax,
and (ii) thermoplastic polymer resin. The compositions of the invention are
especially useful for forming high adsorbent loading thermoplastic
compositions which can be applied using conventional hot melt applicator
equipment and conventional hot melt application conditions. The invention
also encompasses articles such as insulating glass units which include the
thermoplastic adsorbent compositions of the invention.
The adsorbent component used in the compositions of the invention
may be any conventional adsorbent material such as zeolites, silica gels,
activated carbons, silica aluminas, non-zeolite molecular sieves, etc. Non-
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reactive inorganic oxide desiccants are generally preferred. The adsorbent(s)
may be selected to perform a specific function or combination of functions.
Thus, adsorbents adapted to adsorb specific elements, compounds or classes
thereof may be used. Preferably, the adsorbent component contains an
adsorbent such a zeolite A, especially zeolite 3A, which is adapted to
primarily
adsorb water. The adsorbent component may also contain adsorbents designed
to adsorb low molecular weight organic compounds (e.g. zeolite 13X) alone or
in combination with the water-adsorbing adsorbent.
The thermoplastic organic matrix is characterized by the presence of
one or more waxes wherein the wax has a weight average molecular weight of
about 800-10000. The wax should also be compatible with the thermoplastic
resin contained in the organic matrix. That is, the wax should not be prone to
phase separate from the wax/resin combination after blending. The wax
should not have any other adverse interaction with the resin or other
components. The wax is preferably a polymer wax, more preferably an olefin-
containing polymer wax. Most preferably, the wax is an olefin homopolymer
wax such as polyethylene was or polypropylene wax. The wax preferably has
a weight average molecular weight of about 1000-6000, more preferably about
1500-5000. The wax component is believed to impart lower viscosity at
application temperature for the thermoplastic adhesive composition while
avoiding slump or flow of the composition at the actual use temperature.
Preferred waxes are Epolene N- 14 polyethylene wax (M, = 4000) sold by
Eastman Chemical Co. and AC-1702 polyethylene wax sold by Allied Signal
(Mw = 1850). The weight average molecular weights in this application are
based on ASTM D3536-91 using GPC.
In addition to the wax component, the organic matrix contains one or
more thermoplastic resins. The thermoplastic resin preferably comprises one
or more polyolefins resins, e.g., polyethylene, polypropylene, olefin
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copolymers, olefin terpolymers or combinations thereof; however in some
instances other thermoplastic resin systems may also be employed. The
thermoplastic resin has a weight average molecular weight of greater than
10,000, preferably at least about 30,000 more preferably at least about
50,000.
5 The thermoplastic resin preferably has a softening point (ring and ball) of
about 30-200 C, more preferably about 50-150 C. Where the resin is
crystalline, it preferably has a melting point of about 50-250 C, more
preferably about 80-200 C. The thermoplastic resin preferably has a
Brookfield melt viscosity (@ 190 C, spindle #27) of about 150-10,000
centipoise, more preferably about 1,500-8,000 cP. All Brookfield melt
viscosity's specified herein were measured with a Brookfield Thermosel,
model HBDV-III apparatus. A preferred thermoplastic resin is RT-2730
butene copolymer (Mw = 60,000 - 65,000) sold by Rexene Corp.
The organic matrix may also contain auxiliary components such as
tackifiers, coloring agents, scents, lubricants, stabilizers, etc. For most
applications, tackifiers and auxiliary components are preferably kept to a
minimum or are avoided entirely.
The relative amounts of the wax component and the thermoplastic resin
component may be varied depending on the specific wax(es) and resin(s)
selected, the desired adsorbent loading and the desired flowability
characteristics. In general, the wax component acts to promote the flowability
of the composition at application temperature relative to the effect of the
resin
component at a given adsorbent loading. Increased adsorbent loading
generally acts to decrease flowability of the composition at application
temperature for a given organic matrix composition. The overall rheological
characteristics of the thermoplastic adsorbent compositions of the invention
may be varied somewhat depending on the desired application conditions and
end use. Where the end use is as a hot melt desiccant adhesive for use in
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components can be simply loaded into a kneader extruder, twin screw extruder
or other appropriate device to obtain the composition with the desired degree
of desiccant dispersion. The formation of the thermoplastic adsorbent
compositions of the invention is preferably characterized by the absence of
any
solvent.
In these processes, the thermoplastic adsorbent compositions of the
invention can be applied using equipment known for depositing hot melt
adhesives such as equipment manufactured by Airprint Systems Inc., The
Dexter Corp., Nordson Corp., Spraymation, Inc. and others. Using this
equipment, it is possible to deposit the desiccant/organic matrix compositions
of the invention via spraying, rolling, extrusion, etc. Where the compositions
of the invention are to be applied to the spacers of insulating glass units
such
as described in U.S. patents 5,313,761 and 5,177,916, the compositions are
preferably applied using equipment manufactured by Glass Equipment
Development, Inc. The disclosures of U.S. patents 5,313,761 and 5,177,916
are incorporated herein by reference. The compositions of the invention may
also be used in packaging applications such as those described in U.S. Patent
Application Serial No. 08/673,401 filed on June 28, 1996, the disclosure of
which is incorporated herein by reference.
The general method of the applying the compositions of the invention
involves heating the composition to a suitable temperature in order to reduce
its viscosity to a point where the composition can be flowed using the desired
application technique. For example, where the composition is applied by
extrusion on a low speed manufacturing line, a higher viscosity may be usable
compared to higher speed manufacturing lines or where the composition is
applied by spraying or dripping. Typically, the composition will be heated to
about 50-300 C (more preferably about 80-150 C, most preferably about 90-
, 120 C) to affect the necessary viscosity reduction. Once deposited, the
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composition is allowed to cool whereby the composition becomes fixed in the
desired position.
The following examples illustrate some of the compositions of the
invention.
Examnle 1
A thermoplastic adsorbent composition was formed by combining the
following ingredients in a kneader extruder:
Parts by weight
Polyethylene Wax (Epolene N-14) 3.2
Butene Copolymer Resin (RT-2730) 35
Thermal stabilizer (Irganox ' 1010) 0.3
Zeolite 3A (Grace Davison A3) 52
Zeolite 13X (Grace Davison A 10) 5
Gray Pigment (Ti02 + carbon black) 4.5
The composition was tested for its rheological and water adsorptive
properties. The results are reported in Table 1 below. The composition was
tested for water adsorption by determining the equilibrium weight of water
adsorbed at 88 C at 84% R.H. The composition was applied to a metal
substrate at 121 C application temperature and the Lap Shear Adhesion was
measured at 25 C according to ASTM C 961-87. The melt flow was
measured according to ASTM D-1238, Procedure B using a 1.2 Kg load at
124 C. The apparent viscosity was measured according to ASTM test D-
3236-88 at 124 C and 0.125 sec I shear rate using a Brookfield Thermosel,
model HBDV-III apparatus. The ring and ball softening point was measured
according to ASTM E 28-67.
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Example 2
A thermoplastic adsorbent composition was in a manner similar to
Example 1 except that the wax content and adsorbent loading were increased
= as indicated in Table 1. The properties of the resulting material are
reported in
Table 1.
Example 3
A thermoplastic adsorbent composition was in a manner similar to
Example 1 except that the Allied Signal AC- 1702 polyethylene wax was
substituted for Epolene N- 14. The properties of the resulting material are
reported in Table 1.
Comparison Example
A thermoplastic adsorbent composition was prepared as in Example 1
except that no wax was used, and the amount of thermoplastic resin and
adsorbent were increased as indicated in Table 1. The properties of the
resulting material are reported in Table 1. It can be seen that the apparent
viscosity at 124 C is significantly higher in the absence of wax.
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Table I
Example 1 2 3 Comparison
Composition in Weight Percent
RT-2730 35 30 35 36.1
N-14 Wax 3.2 5.2 - -
AC1702 Wax - - 3.2
Zeolite 3A 52 55 52 54
Zeolite 13X 5 5 5 6
Irganox 1010 0.3 0.3 0.3 0.24
Gray Pigment 4.5 4.5 4.5 3.6
Properties
Water Adsorption @ 88 C (wt.%) 11.22 11.9 10.04 10.51
Lap Shear Adhesion (psi) 129.2 142.9 - 130
MFI @ 124 C/1.2 Kg (g/10 min) 15.65 - 16.85 3.695
Apparent Viscosity (10 cP) 1.74 2.27 1.36 4.66
Ring & ball softening point ( C) 122.3 - - 139
